1. Field of the Invention
The invention concerns a method for casting a cylinder head of a piston engine in the region of cooling channels for valve seat rings, wherein a separate core is provided for the cooling channels, and the cooling channel core is mounted in a bottom plate at various points of the bottom plate of a casting mold. Moreover, the invention concerns cooling channels for valve seat rings of a cylinder head of a piston engine, especially cooling channels made according to the invention.
A method for the casting of a cylinder head of a piston engine in the region of cooling channels for valves is known from published, European patent application EP 1 239 135 A2 (corresponding to U.S. patent publication No. 2002/0124815), wherein a separate core is provided for the cooling channels, and the cooling channel core is mounted in a bottom plate at various points of the bottom plate of a casting mold. The cooling channels produced by this method serve, in particular, for improved cooling of the cylinder head in the region of the combustion chamber. The cooling channels are also positioned in the region of two intake valves, two exhaust valves, and one fuel injection nozzle. A feed channel for cooling fluid is connected to a middle cooling channel, which is positioned next to the two exhaust valves between them and the injection nozzle. One end of the middle channel is connected to a drain channel at a crankcase end. The other end of the middle cooling channel emerges into two cooling channels, one of these cooling channels being arranged at the side of the exhaust valve arrangement away from the middle cooling channel and the other cooling channel at the side of the arrangement of the two intake valves away from the middle cooling channel. The outer cooling channels likewise communicate with the drain channels at the crankcase end. Thus, the three cooling channels form a kind of double U arrangement, where the two U-shapes share a leg in common.
The core for the casting of the cooling channels is fashioned in accordance with this arrangement of the cooling channels, so that the core has channels for the passage of the cooling fluid.
European patent EP 0 206 125 B1 describes a cylinder head of a fluid-cooled internal combustion engine, in which a valve ring channel is arranged around each intake and exhaust valve, fully enclosing the valve and emerging into a respective cooling channel.
German patent DE 34 12 052 C2, corresponding to U.S. Pat. No. 4,593,655, describes a cooling device with forced flushing for the cylinder head of an internal combustion engine, in which each valve has a valve seat ring, surrounded by an annular channel, in which a coolant circulates during the operation of the internal combustion engine. The valve seat ring forms part of the wall of the annular channel, so that the coolant comes into direct contact with the valve seat ring. The problem with this arrangement is the sealing off of the valve seat ring from the combustion chamber and from the intake and exhaust channel.
Published, European patent EP 1 329 628 A2 describes a cylinder head with a cooling channel system for a piston engine, especially a large Diesel engine, configured as a two-stroke Diesel engine and having no intake valve. The cylinder head has cooling channels around the respective exhaust valve, one of the cooling channels being arranged concentric to the exhaust valve.